Recently, preparation of nano-sized particles and construction of nano-structure on particle surfaces have been vigorously studied. The effects of surface and interface on nano-sized particles are emphasized, and surface modification is useful to control the characteristics of particles. Information of structure and properties of particle surfaces is necessary to design the surfaces. In this review, characterizations of particle surfaces, especially oxide surfaces, has been discussed. Evaluations of functional groups on the surfaces, mainly hydroxyl groups, and adsorption properties observed by FT-IR have been reviewed. The problems in the specific surface area measurement by gas adsorption have been noted. Fractal analysis of solid surface that is a new concept of surface morphology has been explained.